This invention relates generally to irrigation sprinklers, and, more particularly, to a means for imparting rotary motion to such sprinklers.
The most widely used type of rotary sprinkler includes an oscillating arm having a water deflector at one end arranged to intermittently enter a stream of water ejected by the sprinkler. In an impact drive sprinkler, the arm strikes the body of the sprinkler thereby imparting an increment of rotary motion to the sprinkler, and repeated oscillation of the arm causes the sprinkler to rotate.
The oscillating arm of an impact drive sprinkler includes a centrally upstanding bearing journaled on a vertically disposed pivot pin which is secured to the body of the sprinkler. In order to bias the deflector into the stream of water, a coil spring surrounds the centrally upstanding bearing and is attached at one end to the body of the sprinkler and at the other end to the oscillating arm.
Although the above described devices function satisfactorily, the pivot pin and bearing subject to wear and therefore have a limited useful life. Further, the coil spring must be assembled about the pivot pin and bearing and secured to the body and oscillating arm by hand. In mass production, this time consuming and sometimes difficult operation adds significantly to the cost of manufacturing such sprinklers. Moreover, in order to properly secure the pivot pin to the body while providing the space required for a coil spring, an open frame or bridge portion is generally included on top of the body and adds further to the material required, and therefore to the cost of producing the sprinkler.
Accordingly, there has existed a need for a convenient and effective device for imparting rotational movement to an impact drive sprinkler, which is relatively inexpensive to manufacture and provides an enhanced wear life of the sprinkler with which it is used. As will become apparent from the following, the present invention satisfies that need.